I don't understand how KOP can produce specific angles at the joints in your legs. Seems that the knee angle at KOPS will depend on the lengths of your upper and lower leg, and the ankle angle on the lengths of your lower leg and foot and cleat position. It also seems like hip angle will depend on the above plus torso angle.

The Hogg test is hard to do while riding on the road. I don't have a trainer, which seems like the best way to do the test. I think it is important to be pedaling at a typical force during the test, since the reaction force is part of what keeps your torso from falling. The test is also influenced by core strength. Having said all that, I think the idea/aim is very much correct.